DFT study on electronic and optical properties of graphene under an external electric fieldAbdelhafid Najim, Omar Bajjou, Mustapha Boulghallat, Khalid Rahmani and Lhouceine MoulaouiE3S Web Conf., 336 (2022) 00006DOI: https://doi.org/10.1051/e3sconf/202233600006